Image sensors are used in a wide variety of application, for example, digital cameras, cellular phones, security cameras, as well as various other medical automobile, military, and other applications. As image sensors become ubiquitous in everyday life, the consumers and industry demand image sensors that are faster, smaller, and lower power. In some applications, image sensors must capture images in sequence, and preferably at a high frame-rate. However, conventional image sensors are limited by a variety of factors to produce high quality images at a high frame-rate.
One of the factors that limits the frame-rate of a given image sensor is the speed of conversion circuitry that converts analog pixel signals from a pixel array to digital image values. Within the conversion circuitry, some image sensors rely on Successive Approximation Register (“SAR”) analog-to-digital converters (“ADC”) to convert the analog pixel signals to the digital image values. Therefore, it would advantageous to increase the speed of the SAR ADCs within the conversion circuitry.